The Mitsubishi Lancer Evolution has earned its legendary status through a combination of advanced all-wheel drive and a robust, highly tunable engine. From the 4G63 in the Evo I-IX to the 4B11T in the Evo X, these powerplants respond exceptionally well to modifications. However, every platform has a bottleneck, and for the Evolution seeking that next performance tier, the factory turbocharger is it. Owners quickly find that pushing beyond the 350-wheel-horsepower mark requires a significant upgrade in airflow. The Turbosmart S Series turbocharger has emerged as one of the most refined solutions for this exact power goal, offering a pathway to a reliable and responsive 470 horsepower. This upgrade represents a mature engineering approach to bridging the gap between stock limitations and high-performance aspirations.

Understanding the 350 Horsepower Ceiling

The stock turbocharger on both the 4G63 and 4B11T engines was designed for a specific power band optimized by Mitsubishi. While responsive and durable for factory specifications, it operates near its maximum efficiency at around 350 to 370 wheel horsepower. Increasing boost pressure beyond this point generates excessive heat, forcing the turbo out of its compressor map's efficiency island. The result is high intake air temperatures, increased risk of knock, and diminishing returns on power output. The turbine housing becomes a restriction, creating high backpressure that raises exhaust gas temperatures and places unnecessary stress on the engine. For enthusiasts looking for a reliable daily driver or track weapon, living at the ragged edge of the stock turbo is a compromise. The Turbosmart S Series addresses this directly by providing a compressor and turbine wheel designed to flow efficiently at the 450 to 500 horsepower level.

Turbosmart S Series: Engineering the Upgrade

Turbosmart is renowned for its precision boost control components, and the S Series turbochargers bring that same engineering rigor to the entire rotating assembly. Unlike generic journal-bearing turbos or poorly cast compressor housings, the S Series features a fully billet compressor wheel. Billet wheels are machined from a solid block of aluminum, allowing for complex aerodynamic geometries that cast wheels cannot replicate. This leads to higher efficiency, faster spool, and greater flow capacity. The S Series also incorporates a ported shroud compressor housing, which improves surge margin and allows the turbo to recover boost faster between shifts. For the Evo platform, these features combine to provide a massive power jump from 350 wheel horsepower to the target of 470 wheel horsepower without sacrificing the low-end drivability that makes the car enjoyable on the street.

  • Billet Compressor Wheel: Optimized aerodynamics for high flow and efficiency.
  • Ported Shroud Housing: Reduces turbo lag and improves transient response.
  • High-Flow Actuator: Precise boost control and consistent performance.
  • Durable Construction: Designed to withstand the thermal and mechanical demands of high-horsepower Evo builds.

Ball Bearing vs. Journal Bearing Options

Depending on the specific S Series variant and application, Turbosmart offers configurations that utilize both advanced journal bearings and high-performance ball bearings. For the Evo owner targeting 470 horsepower, a ball-bearing center section is often the preferred choice when immediate response is the priority. Ball bearings significantly reduce rotational inertia compared to traditional journal bearings. This means the turbo spools up faster and reaches full boost earlier in the RPM range. While the initial cost is higher, the improvement in throttle response and the reduction in spool time make it a worthwhile investment for drivers who demand instantaneous power delivery out of corners. The Turbosmart S Series provides this choice without compromising the structural integrity required for sustained high-boost applications.

Detailed Benefits of the S Series Upgrade

Horsepower and Torque Delivery

The headline figure of 470 horsepower is impressive, but how the power is delivered matters just as much. The Turbosmart S Series is designed to produce a wide, flat torque curve. Instead of a violent surge of power that quickly falls off, the S Series holds boost pressure steady to redline. This provides a linear, predictable power band that is easier to control on the street and faster on the track. The increase from 350 to 470 horsepower represents roughly a 35% gain in output. This is not just a peak number; the area under the curve increases dramatically. Where the stock turbo might be gasping for air at 7,000 RPM, the S Series is still pulling hard, extending the usable power band and allowing the driver to hold gears longer. Official Turbosmart S Series product data confirms the focus on mid-range and top-end charge air cooling for maximum power output.

Improved Throttle Response and Transient Boost

One of the most common complaints from owners moving to a larger turbo is lag. The Turbosmart S Series mitigates this through careful wheel design and a compact, efficient housing. The result is throttle response that feels surprisingly close to stock, but with a much harder punch when the boost comes on. Transient response, or the turbo's ability to re-spool after lifting off the throttle and getting back on it, is significantly improved. This is critical for canyon carving or road course driving where the throttle is constantly being modulated. The enhanced airflow dynamics mean that the turbo does not need to "wind up" again; it sits ready to deliver boost the moment the driver demands it. This makes the 470 horsepower figure not just a dyno number, but a usable, accessible part of the driving experience.

Durability and Heat Management

Pushing a stock turbo to 350 horsepower often involves running high boost pressures that generate extreme heat. The Turbosmart S Series is designed to move a larger volume of air more efficiently, which inherently lowers intake temperatures. Lower intake temperatures reduce the risk of detonation and allow the engine's computer to maintain more aggressive ignition timing. Furthermore, the robust construction of the S Series, including a reinforced turbine housing and high-quality wastegate actuator, ensures that the turbo can withstand the thermal loads of repeated hard driving. Discussions on enthusiast forums like EvoM consistently highlight the Turbosmart's reliability under sustained boost, making it a favorite for track-day enthusiasts who prioritize dependability over raw peak numbers.

Critical Supporting Modifications for a Reliable 470 Horsepower Build

A turbocharger cannot work in isolation. To safely and consistently achieve 470 wheel horsepower with the Turbosmart S Series, the supporting modifications must be carefully selected. Skimping on these components will lead to knock, fuel starvation, or mechanical failure.

  • Fuel System: The stock fuel pump and injectors will be at their absolute limit or beyond. A high-flow in-tank fuel pump, such as a Walbro 450 or 525, is mandatory. Upgraded fuel injectors, typically around 1000cc to 1300cc, are required to deliver the necessary fuel volume. For those seeking maximum power and safety, a flex fuel sensor paired with a return-style fuel system allows for the use of E85, which provides significant knock suppression and cooling properties.
  • Engine Management: The factory ECU must be recalibrated. A standalone ECU or a reflash of the stock ECU using a platform like Cobb Tuning's Accessport or EcuFlash is essential. Proper tuning ensures the air-fuel ratios are safe, timing is optimized for the increased airflow, and boost control is dialed in perfectly.
  • Intake and Exhaust Systems: The stock intake snorkel and intercooler piping are restrictive. A full 3-inch or 3.5-inch intake system, a high-flow intercooler core, and a 3-inch turbo-back exhaust are necessary to reduce backpressure and allow the S Series to breathe freely. A quality boost controller, preferably electronic, is also recommended to manage the S Series's wastegate actuator precisely.
  • Drivetrain: 470 horsepower will overwhelm the stock clutch. A twin-disc or upgraded single-disc clutch with a higher torque rating is required to transfer power to the wheels without slipping. The transmission and transfer case fluids should also be upgraded to handle the increased stress.

The Importance of Proper Tuning

The Turbosmart S Series turbocharger provides the hardware, but the software is what brings it to life. A skilled tuner will calibrate fuel maps, ignition timing, and boost control strategy to match the S Series's flow characteristics. With a proper tune, the transition to 470 horsepower feels seamless. The engine pulls cleanly to redline without sudden spikes of boost that can lead to mechanical shock. Tuning also allows the driver to select a power level that suits their needs. The S Series is capable of supporting higher power levels, but tuning it conservatively for 470 horsepower ensures a long engine life. Working with a tuner experienced with the Evo platform is the single best investment an owner can make after installing this turbo kit. A knowledgeable guide on building a reliable 500 horsepower Evo reinforces that the synergy between fueling and tuning is critical for achieving these power goals without sacrificing reliability.

Installation Walkthrough and Technical Considerations

Installing the Turbosmart S Series on an Evo is a project that requires mechanical aptitude, but it is well within the reach of a competent home mechanic. The process is similar to a standard turbo replacement but requires careful attention to oil and coolant routing.

  1. Preparation: Disconnect the battery, drain the engine oil and coolant, and remove the intercooler piping, intake, and downpipe. Access to the turbo is straightforward once these components are out of the way.
  2. Removal of Stock Turbo: Carefully unbolt the stock turbo from the manifold and oil drain flange. This is a good opportunity to replace the oil feed and drain lines with braided stainless steel lines for improved reliability.
  3. Gasket and Flange Preparation: Clean the exhaust manifold and oil drain flanges thoroughly. Use new OEM-quality gaskets to prevent exhaust and oil leaks. Some builders opt to port the exhaust manifold to match the S Series's turbine inlet for optimal flow.
  4. Mounting the S Series: Install the oil drain flange and gasket onto the new turbo. Mount the turbo to the manifold, securing the nuts to the manufacturer's torque specification. Connect the coolant lines and the braided oil feed line.
  5. Interconnecting Systems: Reinstall the downpipe, intercooler piping, intake, and wastegate lines. If using an external wastegate setup, ensure the dump tube is routed properly to avoid grounding out or melting wiring.
  6. Final Checks: Before starting the engine, prime the oil system by disconnecting the crank position sensor and cranking the engine. Reconnect the sensor and start the engine, checking for leaks and proper boost pressure. A professional should verify the tune on a dyno to ensure air-fuel ratios are safe.

Attention to detail during installation prevents common issues such as oil starvation or coolant leaks. Using a quality oil feed restrictor may be necessary depending on the oil pressure of the engine, protecting the turbo's bearings from excessive pressure.

Performance Expectations: Driving the 470 Horsepower Evo

After the installation and tuning are complete, the transformation is immediate. The car feels noticeably stronger across the entire RPM band. At cruising speeds, the turbo is responsive and docile, but planting the throttle instantly summons a surge of power that pins the driver into the seat. The 470 horsepower figure translates to significantly quicker quarter-mile times and faster lap segments. On the street, the passing power is effortless, requiring only a slight increase in throttle position to overtake traffic. The car retains its civility for daily driving while possessing a ferocious top-end pull that the stock turbo simply cannot match. Heat soak is reduced, meaning the car performs consistently even after multiple hard pulls. The improved efficiency of the S Series means that the engine is working less hard to produce the same power, often resulting in better thermal stability and long-term reliability.

Conclusion

The Turbosmart S Series turbo upgrade offers a direct, proven path to transforming a 350 horsepower Evo into a potent 470 horsepower machine. It respects the car's original driving dynamics while unlocking its true potential. By focusing on efficiency, durability, and usable power delivery, this upgrade delivers an exhilarating driving experience. Owners can enjoy the substantial power increase with confidence, backed by the supporting modifications and a professional tune. For those ready to elevate their Evo without compromising reliability, the Turbosmart S Series represents a benchmark solution in the world of high-performance turbocharging.